1. Field of the Invention
The present invention relates to a radio transceiver and, more particularly, to a portable telephone of a digital mobile communication system.
2. Description of the Related Art
A portable telephone|, which permits communication at any time anywhere, is often used in a place where the ambient noise is great, such as in a car or train or on a railway platform. However, the speech encoding system used in digital portable telephones, because it is an encoding system optimizing speech signals, involves the problem that ambient noise included in decoded signals at a receiving side is different from that in wired telephone. Accordingly, a person using the portable telephone hears poor quality sound signals which are uncomfortable to the listener's audio perceptions.